This invention relates to an initial program load (hereinbelow, abbreviated to "IPL") system which loads an electronic computer system with its initial program.
A prior art IPL system has been as shown in FIG. 1. Referring to the figure, numeral 1 designates a central processing unit (hereinbelow, abbreviated to "CPU"), numeral 2 a switch which is built in the CPU 1 and which appoints an IPL device, numerals 3 and 4 magnetic disc devices respectively, and numeral 5 a magnetic tape device. In the following description, it is assumed that the initial program is stored in the magnetic disc device 3, namely, that the magnetic disc device 3 constructs the IPL device. FIG. 2 is a flowchart which shows the flow of IPL operations in the prior art, and in which numerals 20-24 indicate respective steps.
In general, the IPL operations are started by manually actuating the IPL switch. However, in a case where power supply to the computer system has turned "off" for any reason and has thereafter been restarted, the IPL operations are automatically performed. More specifically, the IPL operations are started at the step 20 in FIG. 2. The IPL device 3 is set to start by the step 21, so as to read out the initial program and the IPL operations store it in the CPU 1. At the subsequent step 22, whether or not the readout operation has been normally executed is decided by checking the status of the CPU 1 after the readout, or it is decided depending upon whether or not there is a response from the the IPL device 3 within a predetermined period of time since the start of the readout has been set. When the result of the decision at the step 22 is NO, the operating flow shifts to the step 23, which stops the computer system.
Only in a case where the result of the decision at the step 22 is YES, the operation of the computer system is started by the initial program. That is, under the control of the initial program loaded first, the next program is loaded. This corresponds to the step 24. Before the IPL has been executed, any information is not produced at all, and hence, any program to be utilized does not exist till the end of the load of the least required information. Therefore, the computer system needs to be processed by hardware till then. Accordingly, when the IPL device is abnormal, the continuation of the processing is impossible, and the operating flow cannot avoid shifting to the step 23. Moreover, in some kinds of abnormalities, the computer system repeats the above processing without stopping.
The procedure of the prior art IPL is as stated above. In order to start the IPL again after the step 23, the manual operation must be resorted to. In addition, in a system which is expected to automatically return to normalcy from the momentary interruption of a power source; when the step 23 has been reached due to any fault of the IPL device, the intervention of the manual operation is indispensable. This leads to the disadvantage that, in cases of an unmanned operation etc., it takes a very long time before the system is restarted.